Tubular metallized filament.



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MATTHEW HUNTER, OF SCHENECTADY, NE YORK, ASSIGNOR T GEiNEML ELECTRIC COIYIPANY. A CORPORATION OF NEW YORK.

TUBULAR METALLIZED rILAmEn'r.

1,025,469: Specification of Letters Patent. Patented Edgy 7, 1912, 4 Ho Drawing. I

this new form of filament and a novel proc-.

ess for making the same.

It will be recalled by those skilled in the art that in the manufacture of metallized carbon filaments as usually carried out (and as described in United States Patent #916,905, granted March 30, 1909 to W'illis R. Whitney), a base filament of carbon (usuallv obtained carboni'zation of a squirted filament of cellulose out of contact with air) is given a carbonaceous coating by a flashing or treating process'consisting of heating the filament with current in hydrocarbon vapor and subjected to an extremely high temperature (such as may be obtained in a carbon tube electric furnace), believed 3 to be somewhere in the range of temperature between 2300 and 27009 C. This liring at a high temperature (the so-called metallizing" process) brings about in! pm'tsnt changes in the characteristics of the filament. As the improved properties of the met allized filament'are chiefly due to the ehanges produced in the outer shell by the firing treatment, it will be seen that a filament consisting solely of this modified form a of carbon will possess advantages oycr the composite form of filament resulting from the procedure above set forth.

. According to my invention, Iprrxluce a filament consisting of a tubular shell of 5 metaliized carbon. Such a filament pos 'sesses all the properties of metallizcd carbon, and the absence of a core insures a filo, merit possessed of a high resistance per unit of length. In making this tubular filament 68 I deposit the re alliza'ole coating upon a core consisting of some substance which is refractory enough to bear heating to the temperature necessary in the treat- 51g proc- Application filed September 8, 1908. Serial No. 452,080.

ess but rolatilizable at the high tempera tures obtainable in a carbon tube furnace. 55 If suitable core material is used, the high heat treatment, or metallizing completely eliminates the core, leaving the mctallized shell intact. I have found that titanium -;7*"'*' cal-bid is suitable for use in this manner as a core material. I do not wish, however. to

be limited to the use of this particular ma terial. as other substances, for example, zirconium carbid and other ca'rbids, or even platinum, may also be used.

Although my invention is of general application, I will explain my process with particular reference to the production of a )5 (j tubular filament using titanium carbid for a the core material. "Y'

The novel features of my invention are ,9

pointed out with particularity in the claims appended to this specification.

F or the production of a filament of titanium carbid I make useot the factthat titanium dioxid, when heated in the presence of earbom'undergoes reduction with the formation of titanium carbid and carbon monoxid. The procedure is as follows: pure titanium oxid, TiO. is finely powdered and so mixed with some form of carbor as graphitized lsmpblack, together with a carbonizable binder, suchas glucose. The plastic mixture thus obtained is then squirted into filament-shaped threads. These threads are baked in an oven heated to about 300 (l, whereby'the glucose is carbonized and the "threads made conductive. The threads are then heated, as by means of a current passed through hem, with the resultthat the can bon serves to reduce the oxid with the formation of titanium carbid and liberationof carbon monoxid. If the plastic mixturehas been so compounded to include theoretical quantities of carbon and TiO the chemical ;9b reaction will take place as foliows:--

TiO. +SC:TiC{-2CO Thetitaniuni (illbid filaments so obtained are coherent and iefractouV. These lilu- 10o. mentsare next placed in an atmosphere of. hydrocarbon vapor. such as hen-tin, and

: heated-for about. fire seconds at a temperai-uro of 1500 to 2000" C. which above bright red, host. This heating may be. 210- 10c complishul by pa sing a current directly.

i ar Newsr through the filament in the usual way and produces a deposition of carbon on the titanium ear-hid core. This coating can he built up to any desired thickness. These 5 filaments with a coating of deposited eat-hon forming an outer shell are then pat-lied with flaked graphite in suitable boats, 01' containers, and placed in a metallizing furnace. They are there heated for about twenty 10 minutes at the highest temperature obtainable in a carbon tube furnace," which I should estimate would be about 3500. Upon removal ofithe filament from the metallizing furnace it is found tliat. the titanium earhid core has vaporized, leaving the outer shell intact. This shell is shiny gray in color and very dense and uniform. In fact, it seems to he and undoubtedly is; of the same nature as the shell of an ordinary 20 commercial metallized filament. Such hollow filaments being uniform throughout have the advantage of frccdomfrom thermal strains. The are operatire'at high eilieiency and are otherwise well adapted for general use in incandescent lamps.

\Vhat I claim as new and desire to secure by Letters Patent of the United State 3is- 1. The method of producing a tubular conductor of metallized carbon, which consists in first producing a composite conductor consisting of a vaporizahle core and :1 mctallizalile carbonaceous shell, and then firing said conductor at a temperature suf'licient to vaporize said core and metallize said shell. p 2.1hg methodof producing a tubular -conductorof metallized carbon, which consists in fir t prod'ucing a composite eon du -tor consisting of a core of titanium eart hid and a shell of carbonaceous material, 49 and firing said conductor at a temperature 'suilieient to metallizc the shell of carhonaeeons material and vaporize out the core o titanium earbid.

In "witness whereof, I have hereunto set my hand this 3th day of September. li 'lS.

MAT'llllllV A. llUX'l'E-R.

- \Vitnesses: Y

BENJAMIN B. HULL,

Copies of this patent may be obtained for 'five cents each, by addressing the Commissioner of Patents, Washington, D. G." 

